Methods and apparatus for EMI shielding

ABSTRACT

Disclosed are methods and apparatus for improving the resiliency and airflow through a honeycomb air vent filter while providing EMI shielding. In one embodiment, the honeycomb can be manufactured from a dielectric (e.g., plastic) substrate to provide improved resistance to deformation as compared to conventional aluminum honeycomb. The dielectric honeycomb substrate is metallized to provide EMI shielding capability. The metallized honeycomb substrate is cut slightly oversize to fit an opening in an electronic enclosure, which results in elastic deformation of resilient perimeter spring fingers that are used to hold the metallized dielectric honeycomb in place and provide electrical conductivity between the metallized dielectric substrate and the enclosure, thereby eliminating the use of a frame. In another embodiment, additional conductive layers can be added to the metallized dielectric honeycomb. In yet another embodiment, the metallized dielectric honeycomb substrate can be utilized in a framed configuration to provide improved durability.

CROSS-REFERENCE TO RELATED APPLICATIONS

More than one reissue application has been filed for the reissue of U.S.Pat. No. 6,870,092. The reissue applications are the present divisionalreissue application and application Ser. No. 11/516,803, filed Sep. 5,2006, now Reissue RE41,594. This application is a divisional applicationfrom U.S. reissue application Ser. No. 11/516,803, now Reissue RE41,594,which, in turn is a reissue of U.S. Pat. No. 6,870,092, which issuedfrom U.S. patent application Ser. No. 10/310,107 filed on Dec, 4, 2002,which, in turn claims the benefits of U.S. Provisional Application Ser.No. 60/336,609, filed on Dec. 4, 2001, and U.S. Provisional ApplicationSer. No. 60/378,886, filed on May 8, 2002, the disclosures of which areincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to methods of manufacturing electromagneticinterference (“EMI”) shields and the EMI shields produced thereby.

BACKGROUND OF THE INVENTION

As used herein, the term EMI should be considered to refer generally toboth EMI and radio frequency interference (“RFI”) emissions, and theterm electromagnetic should be considered to refer generally toelectromagnetic and radio frequency.

During normal operation, electronic equipment generates undesirableelectromagnetic energy that can interfere with the operation ofproximately located electronic equipment due to EMI transmission byradiation and conduction. The electromagnetic energy can be of a widerange of wavelengths and frequencies. To minimize the problemsassociated with EMI, sources of undesirable electromagnetic energy maybe shielded and electrically grounded. Shielding is designed to preventboth ingress and egress of electromagnetic energy relative to a housingor other enclosure in which the electronic equipment is disposed. Sincesuch enclosures often include vent openings and gaps or seams betweenadjacent access panels and around doors, effective shielding isdifficult to attain, because the gaps in the enclosure permittransference of EMI therethrough. Further, in the case of electricallyconductive metal enclosures, these gaps can inhibit the beneficialFaraday Cage Effect by forming discontinuities in the conductivity ofthe enclosure which compromise the efficiency of the ground conductionpath through the enclosure. Moreover, by presenting an electricalconductivity level at the gaps that is significantly different from thatof the enclosure generally, the gaps can act as slot antennae, resultingin the enclosure itself becoming a secondary source of EMI.

Specialized EMI gaskets have been developed for use in shielding smallgaps in electronic enclosures. These include, but are not limited to,metal spring fingers, wire mesh, fabric-over-foam, and conductiveelastomers. To shield EMI effectively, the gasket should be capable ofabsorbing or reflecting EMI as well as establishing a continuouselectrically conductive path across the gap in which the gasket isdisposed.

One particularly challenging shielding issue on electronic enclosures isthe ventilation opening. In many enclosures, openings that are muchlarger than gaps along seams and I/O ports are intentionally placed inthe enclosures to facilitate the removal of heat. Without EMI shielding,the openings represent huge EMI leakage points. One common approach toshielding these areas is to use ventilation panels, also known as ventpanels. Traditional vent panels consist of a metallic honeycomb materialmechanically assembled into a stiff metallic frame. This assembly isthen fastened to the enclosure with some type of EMI gasketing installedalong the enclosure/vent panel interface. The vent panels can be used inthe as-manufactured state or they can be plated. Lower cost vent panels,which are usually made of aluminum honeycomb, provide lower levels ofshielding effectiveness and are not structurally robust. In applicationsthat require a very robust vent panel, which also provides very highlevels of shielding effectiveness, steel or brass honeycomb is oftenused. These products, however, are much more expensive.

A key attribute of any vent panel is the ease of airflow through thehoneycomb, because cooling capability is directly related to volume ofairflow per unit of time. Also, in traditional vent panels, electricalcontact is made by mechanically crimping the metal frame against thehoneycomb material, such that the metal frame causes an indentation ofthe honeycomb material along the edge of the frame. This insures goodelectrical contact as long as the frame is not subjected to severebending or torque.

Enclosures for electronic equipment use airflow to remove heat from theenclosures. Honeycomb filters can be installed in an opening on theenclosure to serve as ventilation panels. In addition, honeycomb filtersalso provide EMI shielding. Examples of commercially available honeycombfilters are designated “Commercial Honeycomb Ventilation Panels” and “BE11 ALU-HONEYCOMB FILTERS” air ventilation panels manufactured by LairdTechnologies, Inc. (f/k/a Instrument Specialties Co. and AdvancedPerformance Materials). Another example of commercially availablehoneycomb filters are designated RF CORE honeycomb cores manufactured byR & F Products, located in San Marcos, Calif. Other similar commerciallyavailable ventilation panels are manufactured by Tecknit located inCranford, N.J., and Chomerics located in Woburn, Mass.

As shown in FIG. 1, commercially available vent panels 10 typicallyinclude a honeycomb substrate 12 and a frame 14. The honeycomb substrate12 is typically made out of very thin strips of corrugated aluminum. Inmost cases glue, spot welds, or other attachment methods are used tohold the honeycomb substrate 12 together. Piercings are often madebetween the aluminum layers to improve electrical conductivity. Theelectrically conductive aluminum honeycomb substrate 12 may optionallybe covered with a conductive layer to enhance electrical conductivityacross the honeycomb substrate 12. Some examples of conductive layersare an aluminum chromated layer or a tin plated layer. These coatingsmay also be added to enhance corrosion resistance.

As shown in partial cross-section in FIG. 2, the frame 14 is crimpedonto the honeycomb substrate 12. The frame 14 includes solid pincherfingers 16 to grip the honeycomb substrate 12. The frame 14 andhoneycomb substrate 12 are in electrical communication with each otherso EMI emissions captured by the honeycomb substrate 12 can betransferred from the honeycomb substrate 12 to the frame 14 andultimately to the electronic enclosure. The design of these pincherfingers 16 results in a line contact between the frame 14 and thehoneycomb substrate 12. This feature can make the vent panel 10susceptible to localized EMI leakage if twisting and jarring of the ventpanel 10 degrades that contact area. In addition, the need for thepincher fingers 16 in the metal extrusion limits how narrow the frame 14can be manufactured, typically not less than 0.25 inch wide.

As shown in FIG. 3, the vent panel 10 is installed in an opening 18formed in an enclosure 20 for electronic equipment. An EMI gasket 22 isattached to the vent panel 10 about a perimeter thereof to seal EMIleakage paths between the enclosure 20 and the vent panel 10.

The vent panel 10 allows air to flow through the honeycomb substrate 12to ventilate and cool the electronic equipment inside the enclosure 20.As electronic applications achieve higher clock speeds, and aselectronic components are more compactly packed in the enclosure 20, theheat generated within the enclosure 20 increases, necessitating higherairflow. However, airflow through the vent panel 10 is limited by thepresence of the frame 14. Depending on the design of the vent panel 10,the presence of the frame 14 can reduce airflow through the opening 18by about 5% to 15% or more. Traditional frames, with the pincher fingerfeature, greatly limit the ability to increase vent panel airflow due tothe minimum width requirements of the frame material.

Another problem with commercially available vent panels 10 is that theyare typically made of aluminum, which is not very resilient andtherefore subject to damage. The lack of resiliency results in plasticdeformation of the honeycomb filter due to impacts that can beencountered during assembly and field use. To ensure proper airflowafter damage, cells of the honeycomb have to be reworked. The reworkprocess is time consuming, requiring the deformed aluminum strips to bebent to open the cells. Even with rework, there is typically degradationof flow through the vent panel 10. In addition, the rework often resultsin an aesthetically undesirable appearance. There is a need for ahoneycomb filter with improved airflow capability and improveddurability.

SUMMARY OF INVENTION

One purpose of this invention is to provide improved durability to EMIshielding honeycomb filters. Another purpose of this invention is toprovide improved airflow through EMI shielding honeycomb filters.

In one aspect, the invention relates to a vent panel adapted to shieldagainst EMI, the vent panel including a dielectric panel having athickness defined by a first side and a second side. The dielectricpanel defines a number of apertures. The vent panel also includes afirst electrically conductive layer applied to the dielectric panel. Theresulting conductively coated, or metallized, dielectric panelattenuates a transfer of electromagnetic energy from a first side of thepanel to a second side of the panel.

In one embodiment, the dielectric panel is formulated from a polymer,such as acrylonitrile-butadiene-styrene (ABS), polycarbonates,polysulfones, polyamides, and polypropylenes. In another embodiment, thedielectric panel includes a plurality of tubes or other shapes fastenedtogether. In another embodiment, the dielectric panel includes aplurality of tubes or other shapes co-extruded together. In yet anotherembodiment, the dielectric panel is manufactured by injection molding.

In one embodiment, the electrically conductive layer includes a firstlayer selected from the group consisting of copper, nickel, tin,aluminum, silver, graphite, bronze, gold, lead, palladium, cadmium, zincand combinations thereof. In another embodiment, the electricallyconductive layer includes a second electrically conductive layer, whichmay consist of the same or a different conductive material in electricalcommunication with the first electrically conductive layer.

In one embodiment, the plurality of apertures are configured as atwo-dimensional array of like apertures, each aperture having across-sectional shape, such as a circle, a hexagon, a rectangle, etc.The vent panel includes a conductive edge extending substantially aboutthe perimeter, being adapted for placing the vent panel into electricalcommunication with the chassis in which the vent panel is mounted. Insome embodiments, the conductive edge also mechanically secures the ventpanel within an aperture in the chassis. For example, the conductiveedge can include resilient spring fingers, dimples, and combinations ofthese provided along a band extending about the perimeter. The resilientspring fingers and dimples compress against an opposing mating surfaceof the chassis upon installation, thereby providing electrical contact.

In another aspect, the invention relates to a method for manufacturing avent panel adapted to shield against EMI. The suitably adapted ventpanel is manufactured by providing a dielectric panel having a thicknessdefined by a first side and a second side, and defining an array ofapertures. A first electrically conductive layer is applied to thedielectric panel.

In one embodiment, a first conductive layer is applied using one or moreof electroless plating, radio-frequency sputtering, direct-currentsputtering, or physical deposition. In some embodiments, a secondelectrically conductive layer is applied using the same or a differentplating method.

In one embodiment, the dielectric panel is provided by fastening anumber of dielectric tubes together. In another embodiment, thedielectric panel is provided by co-extruding together a number of tubes.In another embodiment, the dielectric panel is provided by injectionmolding. And, in yet another embodiment, the dielectric panel isprovided by machining.

In one embodiment, the conductively coated dielectric panel is taperedto provide a snug mechanical fit also having good electrical contact. Inanother embodiment, the dielectric panel is selectively cut along itsedges to provide a “spring-finger” action that together with whole cellsalong its perimeter provides a snug fit by compressing the cells and/orportions of cells along its perimeter. In another embodiment, aconductive strap having compressible fingers and/or dimples is appliedto the perimeter of the metallized dielectric vent panel such that thecompressible fingers an/or and/or dimples make contact with an opposingsurface, for example a chassis, thereby providing a snug mechanical fitand good electrical contact.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further advantages of this invention may be betterunderstood by referring to the following description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic drawing of a conventional aluminum air filter;

FIG. 2 is a schematic drawing of a partial cross-section of an aluminumhoneycomb substrate and a frame for the conventional aluminum airfilter;

FIG. 3 is a schematic drawing of the conventional aluminum air filterinstalled in an opening in an enclosure for electronic equipment;

FIG. 4 is a schematic drawing depicting a perspective view of across-section of a metallized dielectric honeycomb filter;

FIG. 5 is a flow diagram illustrating an embodiment of a process forpreparing certain embodiments of the invention;

FIG. 6A is a schematic drawing of another metallized dielectrichoneycomb filter;

FIG. 6B is an exploded view of a cell from the metallized dielectrichoneycomb filter in FIG. 6A;

FIG. 7A is a schematic drawing of a metallized dielectric honeycombfilter installed horizontally in an opening in an enclosure forelectronic equipment;

FIG. 7B is a cross-section of the metallized dielectric honeycomb filterinstalled horizontally in an opening in an enclosure for electronicequipment taken along section 7B-7B of FIG. 7A;

FIG. 7C is a schematic drawing of a metallized dielectric honeycombfilter, angled in the thickness direction, installed vertically in anopening in an enclosure for electronic equipment;

FIG. 7D is a cross-section of the metallized dielectric honeycombfilter, angled in the thickness direction, installed vertically in anopening in an enclosure for electronic equipment taken along section7D-7D of FIG. 7C;

FIG. 7E is a cross-section of an alternative embodiment of themetallized dielectric honeycomb filter having a rabbet edge along itsperimeter, installed vertically in an opening in an enclosure forelectronic equipment taken along section 7D-7D of FIG. 7C;

FIG. 7F is a schematic drawing of metallized dielectric honeycombfilters, angled in the thickness direction, installed vertically andanother filter installed horizontally in an enclosure for electronicequipment;

FIG. 7G is a schematic drawing of a tapered metallized dielectrichoneycomb filter installed horizontally in an opening in an enclosurefor electronic equipment;

FIG. 7H is a cross-section of the tapered metallized dielectrichoneycomb filter installed horizontally in an opening in an enclosurefor electronic equipment taken along section 7H-7H of FIG. 7G;

FIG. 7I is a schematic drawing of a tapered metallized honeycomb filterinstalled horizontally in one opening in an enclosure for electronicequipment;

FIG. 8A is a schematic drawing illustrating a top view of a band framesurrounding a metallized dielectric honeycomb vent panel in which theband frame has horizontal spring fingers;

FIG. 8B is a schematic drawing illustrating a front view of the bandframe in which the band frame has horizontal spring fingers;

FIG. 8C is a schematic drawing illustrating a side view of the bandedframe in which the band frame has horizontal spring fingers;

FIG. 8D is a schematic drawing illustrating a front view of analternative band frame in which the band frame has vertical springfingers;

FIG. 8E is a schematic drawing illustrating a side view of thealternative frame in which the band frame has vertical spring fingers;

FIG. 8F is a schematic drawing illustrating a top view of a band framesurrounding a metallized dielectric honeycomb vent panel in which theband frame has elongated dimples;

FIG. 8G is a schematic drawing illustrating a front view of the bandframe in which the band frame has elongated dimples;

FIG. 8H is a schematic drawing illustrating a side view of the bandframe in which the band frame has elongated dimples;

FIG. 8I is a schematic drawing illustrating a top view of an alternativeband frame surrounding a metallized dielectric honeycomb vent panel inwhich the band frame has circular dimples;

FIG. 8J is a schematic drawing illustrating a front view of thealternative band frame in which the band frame has circular dimples;

FIG. 8K is a schematic drawing illustrating a top view of a metallizeddielectric honeycomb vent panel surrounded by a slim profile frame inwhich the frame has small horizontal edge tabs and spring fingers;

FIG. 8L is a schematic drawing illustrating a front view of the slimprofile frame in which the frame has small horizontal edge tabs andspring fingers;

FIG. 8M is a schematic drawing illustrating a side view of the slimprofile frame in which the frame has small horizontal edge tabs andspring fingers;

FIG. 9 is a schematic drawing illustrating a side view of an embodimentof a metallized dielectric honeycomb vent panel surrounded by acompressible elastomer EMI gasket;

FIG. 10 is a plot of EMI shielding test results for metallizeddielectric honeycomb filters in accordance with certain embodiments ofthe invention; and

FIG. 11 is a plot of airflow test results for metallized dielectrichoneycomb filters in accordance with certain embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, honeycomb filters used for airflowand EMI shielding can have improved airflow and durability through theuse of a metallized dielectric honeycomb substrate and a framelessfilter design. Metallized dielectric honeycomb substrate utilized in areduced frame design can also be used to provide even greater durabilityalong with increased airflow.

FIG. 4 shows in perspective view, a cross-section of one embodiment of ametallized dielectric honeycomb filter 50. The metallized dielectrichoneycomb filter 50 includes a dielectric honeycomb substrate 52 and aconductive layer 54. As used herein, the term honeycomb refers to atwo-dimensional array of apertures of arbitrary cross-section. Theaperture cross-section can be any shape, such as hexagonal, circular,elliptical, square, rectangular, triangular, rhomboidal, or other, andcombinations thereof. The dielectric honeycomb substrate 52 is selectedto provide significantly improved resiliency as compared to conventionalaluminum honeycomb filters. Due to the improved resiliency, thedielectric honeycomb substrate 52 is much less likely to be deformedpermanently under load or impact conditions that can be encounteredduring assembly and normal operation. By minimizing the possibility ofdeforming through the use of the dielectric honeycomb substrate 52, muchof the rework required to fix damaged aluminum honeycomb filters inorder to maintain proper airflow through the filter is therebyeliminated.

The dielectric honeycomb substrate 52 can be made out of any dielectricmaterial, such as plastic. For example, some materials that can be usedfor the dielectric honeycomb substrate 52 areacrylonitrile-butadiene-styrene (ABS), polycarbonates, polysulfones,polyamides, polypropylenes, polyethylene, and polyvinyl chloride (PVC).Additionally, other dielectric materials may be used such as fiberglassand paper products, such as aramid (e.g., Kevlar®) sheets, and aramidfiber paper. Dielectric honeycomb substrates are commercially available.For example, Kevlar® honeycomb cores (e.g., Ultracor part no. PNUKF-85-1/4-1.5), carbon honeycomb cores (e.g., Ultracor part no.UCF-145-3/8-0.8) are commercially available from Ultracor Inc., locatedin Livermore, Calif., Aramid fiber honeycomb cores (e.g., Hexcel partno. PN HRH-10), fiberglass honeycomb cores (e.g., Hexcel part no. HRP)are commercially available from Hexcel Corp., located in Danbury, Conn.,and polypropylene honeycomb cores (e.g., Plascore part no. PP30-5) arecommercially available from Plascore, Inc., located in Zeeland, Mich.

The dielectric honeycomb substrate 52 can have cells 53 sized to meet aparticular application. The substrate 52 can be described as having anoverall length, L, and an overall width, W. The dimensions L and W aretypically determined by a particular application, generally matching thedimensions of an aperture to be shielded. Each one of the cells 53 canbe described as having a cross-section diameter, d, and a thickness, t.The dimensions (d, t) for a cell 53 are generally selected to provide apredetermined level of EMI performance, often referred to as shieldingeffectiveness. Each cell, in essence, represents a waveguide that willgenerally pass EMI having wavelengths, (λ_(EMI)), less than a cutoffwavelength, λ_(c), (i.e., high frequencies) while rejecting EMI havingwavelengths greater than λ_(c) (i.e., low frequencies).

A general relationship, presented in equation 1, can be defined forapproximating the shielding effectiveness in terms of the abovegeometric parameters, for an individual cell, measured in decibels (dB).A geometry-dependent constant K is approximately 32 for circular cells,and 27 for rectangular cells.

$\begin{matrix}{{Shielding\_ Effectiveness}_{d\; B} \approx {K\frac{t}{d}\sqrt{\left( {\lambda_{EMI}/\lambda_{c}} \right)^{2} - 1}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

Typically, the cell diameter, d, can range from about 0.06 inches toabout 1.0 inch, while the cell thickness, t, can range from about 0.125inch to 1.5 inches with common depths of 0.25 inch to 1 inch.

The density of the dielectric honeycomb substrate 52 can range fromabout 2 lb/ft³ to about 20 lb/ft³. By selecting a lower densitydielectric honeycomb substrate 52, the flexibility of the dielectrichoneycomb substrate can be increased, which generally decreases springforce in the honeycomb substrate 52. Typical wall thickness range offrom 0.002 inch to 0.05 inch, but are not limited to this range. Forapplications where a more rugged dielectric honeycomb substrate 52 isrequired, a higher density dielectric honeycomb substrate 52 or adifferent honeycomb geometry can be selected.

To manufacture a vent panel according to the invention, in oneembodiment referring now to FIG. 5, a dielectric vent panel, such as thehoneycomb substrate 52 described above, is provided (step 60). Thehoneycomb substrate 52 can be prepared by extrusion or by molding (e.g.,injection molding) as an integral element. Such molding techniques arewell adapted for polymer substrates. Alternatively, the honeycombsubstrate 52 can also be manufactured by bonding or otherwise attachingtogether a plurality of corrugated strips. Such bonding techniques arewell adapted to substrates formed from a fibrous material, such aspaper, as well as polymer substrates. Alternatively, a number of tubes,each tube forming one of the cells 53, can be fastened together in aplanar array, such that a longitudinal axis of each of the tubes isgenerally parallel with the axes of its neighboring tubes. The fasteningcould be achieved using a chemical bond, such as a glue, a thermal weld,or a mechanical bond, such as a crimp. The honeycomb substrate 52 canalso be manufactured by other methods, such as machining a sheet of thesubstrate material, for example by boring each of the cells 53 using adrill, or cutting each using a die.

Next, the dielectric honeycomb substrate 52 can be shaped into anydesired configuration (step 62). For example, a planar dielectricsubstrate 52 can be configured in any desired planar shape, such as asquare, a rectangle, a circle, etc., having predetermined dimensions toconform to an intended aperture. Such overall shaping can be performedduring the manufacturing stage of the substrate 52, for example byselectively altering the shape of a mold, or extruder. The shaping canalso be performed post-manufacturing. For example, the substrate 52 canbe cut using a knife, a saw, shears, a laser, or a die. Additionally,certain dielectric substrates, such as polymers, lend themselves to avariety of machining techniques. For example, a dielectric honeycombsubstrate 52 can be machined to shape one or more of its edges along itsperimeter to include a bevel, or a rabbet. Still further, the dielectricsubstrate 52 can be shaped to include a convex or concave surface orindentation over a portion of either or both of its planar surfaces.Such a planar surface deformation may be desired, to accommodate amechanical fit.

In order to provide EMI shielding, a conductive layer 54 is applied tothe dielectric honeycomb substrate 52, resulting in the metallizeddielectric honeycomb filter 50. In one method, a first conductive layeris applied to the dielectric honeycomb substrate 52 (step 64). The firstconductive layer can be applied using a variety of techniques known tothose skilled in the art, such as electroless plating or physical vapordeposition. See, for example, U.S. Pat. No. 5,275,861 issued to Vaughnand U.S. Pat. No. 5,489,489 issued to Swirbel et al., the disclosures ofwhich are herein incorporated by reference in their entirety. Forexample, a conductor, such as copper, can be applied using anelectroless bath as taught by Vaughn.

The electroless bath method is particularly well suited for a class ofpolymers known as plateable plastics. This class of plastics includesacrylonitrile-butadiene-styrene (ABS) and polycarbonates, along withother polymer compounds, such as polysulfones, polyamides,polypropylenes, polyethylene, and polyvinyl chloride (PVC). Generally,the dielectric honeycomb substrate 52 should be pretreated to remove anyimpurities (e.g., dirt, and oil). Depending on the type of material, thesubstrate 52 may be treated still further to enhance its adhesionproperties with the initial conductive layer. For example, the surfacecan be abraded by mechanical means (e.g., sanding or sandblasting) or bya chemical means (e.g., by using a solvent for softening or an acid foretching). A chemical pretreatment can also be added to alter thechemistry of the surface, further enhancing its ability to chemicallybond to the first layer.

Other methods of applying the first conductive layer include applying aconductive paint, such as a lacquer or shellac impregnated withparticulate conductors, such as copper, silver, or bronze. Still othermethods of applying the first conductive layer include physicaldeposition, such as evaporation, non-thermal vaporization process (e.g.,sputtering), and chemical vapor deposition. Sputtering techniquesinclude radio-frequency (RF) diode, direct-current (DC) diode, triode,and magnetron sputtering. Physical vapor deposition includes suchtechniques as vacuum deposition, reactive evaporation, and gasevaporation.

Depending on the desired thickness and/or coverage, the step of applyingthe first conductive layer can be optionally repeated (step 66), suchthat one or more additional conductive layers, being made ofsubstantially the same conductor, are applied to the previously-treatedsubstrate 52, thereby increasing the thickness of the layer. Inrepeating the application of the conducting layer, generally the samemethod of plating can be used; however, a different method can also beused.

Generally, any conductive material can be used for the conductive layer54. Some examples of metals that can be used for the conductive layer 54are copper, nickel, tin, aluminum, silver, graphite, bronze, gold, lead,palladium, cadmium, zinc and combinations or alloys thereof, such aslead-tin and gold-palladium. The conductive layer 54 can also be applieddirectly as a conductive compound. For example, the substrate 52 can betreated with a single electroless bath having both copper and nickel.The resulting conductive layer 54 is a compound of both copper andnickel.

Optionally, more than one type of conductive layer can be applied to thehoneycomb substrate 52 (step 68). For example, after the initialconductive layer 54 has been applied, one or more additional conductivelayers of the same, or different material, can be applied usingelectroless plating, electrolytic plating, physical vapor deposition, orother methods known to those skilled in the art (step 70). Electrolyticplating would generally be available for applying subsequent conductinglayers, as the initial conducting layer would provide the requisitesurface conductivity.

In one embodiment, a second conductive layer of nickel is applied over afirst conductive layer of copper, the copper providing a relatively highelectrical conductivity and the nickel providing a corrosion resistanttop coat. As with the initial conductive layer 54, and for similarreasons, the second type of conductive coating can be optionallyreapplied until a desired thickness is achieved.

Additional layers of coating or treatment of still other different typesof conductive, or even non-conductive materials can be optionallyapplied to the metallized dielectric honeycomb filter 50 (step 72). Forexample a fire retardant, a mildew inhibitor, or an anti-corrosiontreatment can be applied to the metallized dielectric honeycomb filter50. These coatings can be selectively applied either covering the entiresurface, or any portion thereof. For example, the metallized dielectrichoneycomb filter 50 can be completely immersed in a fire retardant, orselectively treated with a corrosion inhibitor, using a maskingtechnique such that a perimeter of the filter 50 remains untreated,thereby avoiding any reduction in the quality of the achievableelectrical contact.

Further, the metallized, treated filter 50 can again be shaped, asrequired, by any of the previously disclosed techniques (step 74). Also,an edge treatment can be optionally applied to the perimeter or mountingsurface of the filter 50 (step 76). Particular edge treatments includecommercially available EMI gaskets, including metallized spring fingers,conductive fabrics, conductive elastomers, wire mesh, conductive foam,and conductive fabric coated elastomers.

FIG. 6A shows another embodiment of metallized dielectric honeycombfilter 50. In this embodiment, the dielectric honeycomb substrate 52′ isformed by a plurality of tubes 55, which can be co-extruded together. Inanother embodiment, the plurality of tubes 55 can be bonded together.This type of structure could also be produced by injection molding orsimilar plastic manufacturing processes. The dielectric honeycombsubstrate 52′ is then metallized as previously described.

FIG. 6B is an exploded view of a cell 53′ from FIG. 6A, which shows theconductive layer 54 on the dielectric honeycomb substrate 52′ of cell53′. Again, the conductive layer 54 can be applied by any of thetechniques previously described.

In order to provide improved airflow, reduce costs, and simplifymanufacture, the metallized dielectric substrate 50, referring again toFIG. 4, does not have a frame, so that a larger percentage of thesurface area of the metallized dielectric substrate 50 can accommodateairflow through the opening 18 in the enclosure 20. The metallizeddielectric honeycomb filter 50 can be easily cut to fit the size of theopening 18 in the enclosure 20. Alternatively, the dielectric honeycombsubstrate 52 can be cut to size prior to adding the conductive layer 54.Cutting the metallized dielectric honeycomb filter 50 through the cells53 results in partial, open sided honeycomb cells 86 bounded in part bycell walls forming resilient spring fingers 88. The resilient springfingers 88 elastically deform when the filter 50 is installed so as toboth ensure electrical contact with the enclosure 20 and hold themetallized dielectric honeycomb filter 50 firmly in place. Thus, thespring fingers 88 form a conductive edge extending substantially aboutthe perimeter of the filter 50 for placing the filter 50 into electricalcommunication with the enclosure 20.

The cylindrical tubes 55 that make up the cells 53 of the metallizeddielectric honeycomb filter 50, shown in FIG. 6A, can also be made veryflexible so as to elastically deform when the metallized dielectrichoneycomb filter 50 is installed and thereby ensure electrical contactwith the enclosure 20. Electrical contact is ensured with the resilientspring fingers 88′ formed by cutting cells 53′ on the perimeter of themetallized honeycomb filter 50. In addition, by eliminating theconventional frame, the costs associated with manufacturing the filterare reduced.

The cells 53 can be cut along their diameter, leaving an approximatelysemicircular cell portion, as shown. Alternatively, the cells 53 can becut leaving either a greater or lesser amount of the cell wall to form aspring.

FIG. 7A shows how the metallized dielectric honeycomb filter 50 would beinstalled in a channel 91 located in an electronics cabinet in ahorizontal mounting configuration. A door member or final cap 92encloses the metallized dielectric honeycomb filter 50 in the channel91. In this configuration, all of the mounting surfaces of the cabinetand vent panel are orthogonal. The metallized dielectric honeycombfilter 50 can be sized such that the resilient spring fingers 88elastically deform and fit snugly in the channel 91 to ensure a tightfit and good electrical contact. By using the channel 91 integrallyformed in the enclosure 20, the need for a separate EMI gasket betweenthe filter 50 and enclosure 20 is eliminated. FIG. 7B is a cross-sectionof the metallized dielectric honeycomb filter 50 installed horizontallyin the opening in an enclosure for electronic equipment taken alongsection 7B-7B of FIG. 7A.

In yet other embodiments, shown in FIG. 7C-7I, the opening 18 can betapered either vertically (having different surface areas comparing fromtop to bottom), or horizontally (having different width measurementscomparing the front and rear edges). In a vertical configuration, shownin FIG. 7C, the frameless metallized dielectric honeycomb filter 50 willhave a taper along its thickness, which would be similar to the taper inthe cabinet wall. The metallized dielectric honeycomb filter 50 would beinserted into the tapered cabinet opening (alternatively, the cabinetcan include non-tapered, or straight edges) at about a 90 degree angleto the plane of the opening until an intimate compression fit (similarto a cork) is achieved. Stops can optionally be placed above and/orbelow the vent panel to keep it in place during usage. FIG. 7Dillustrates a cross-section of the metallized dielectric honeycombfilter 50, angled in the thickness direction, installed vertically in anopening in an enclosure for electronic equipment taken along section7D-7D of FIG. 7C. FIG. 7E illustrates an alternative embodiment in whichthe perimeter of the filter 50′ is shaped to provide a rabbet edge 94 toaccommodate a suitable mating surface 91′. Again, stops can optionallybe placed above the vent panel to keep it in place during usage. FIG. 7Fshows the metallized dielectric honeycomb filter 50, with taper or arabbet along its thickness, installed on the top surface 20A, and a wall20B of an electronic equipment enclosure 20.

FIG. 7G shows the horizontal configuration, where the framelessmetallized dielectric honeycomb filter 50 will have a taper along itslength, which is similar to a taper in a cabinet channel 91 adapted forreceiving a tapered filter 50. As illustrated, the filter 50 has a firstwidth W₁ along a front edge, and a different second width, W₂, along arear edge. The metallized dielectric honeycomb filter 50 is insertedinto the cabinet channel 91 in the place of the filter and along thechannel axis until the metallized dielectric honeycomb filter 50 is snugalong both side walls 93′ and rear wall 93″. A final cap or door member92 can be clamped or otherwise attached over the metallized dielectrichoneycomb filter 50 to seal the final side. FIG. 7H illustrates across-section of the tapered metallized dielectric honeycomb filter 50installed horizontally in an opening in an enclosure for electronicequipment taken along section 7H-7H of FIG. 7G. FIG. 7I illustrates ametallized dielectric honeycomb filter 50 with a taper along its lengthinstalled in an electronic equipment enclosure 20.

In other embodiments, shown in FIGS. 8A-8M, a band frame or slim profileframe 96′, 96″, 96′″, 96″″, generally 96, is added to the metallizeddielectric honeycomb filter 50. In the band frame configuration, shownin FIGS. 8A-8M, a flat metal strip 98′, 98″, 98′″, 98″″, generally 98,with numerous spring fingers 100′, 100″, generally 100, (FIGS. 8A-8E) ordimples 101′, 101″, generally 101, (FIGS. 8F-8J) along its length iswrapped tightly around the perimeter of the metallized dielectrichoneycomb filter 50 on its thickness side forming a band 96′, 96″, 96′″,96″″ generally 96. The band 96 on its interior, flat side, compressesthe metallized dielectric honeycomb filter 50 along its thickness tocreate good electrical contact, while the spring fingers 100/dimples 101on the opposite, exterior side of the band 96 make good electricalcontact with the cabinet (generally attaining a resistance value belowsome predetermined desirable threshold value). The features on the band96 are oriented appropriately depending on whether the metallizeddielectric honeycomb filter 50 is inserted vertically (FIGS. 8D and 8E)or horizontally (FIGS. 8B and 8C) with respect to a cabinet opening. Thebenefit of this band frame 96 is that it leaves the airflow surface ofthe metallized dielectric honeycomb filter 50 virtually unblocked whileincreasing the flexibility of the vent panel.

FIG. 8B is a schematic drawing illustrating a front view of one side ofthe band frame 96 96′ of FIG. 8A, where the band frame has horizontalspring fingers 100′. FIG. 8C is a schematic drawing illustrating a sideview of one side of the band frame 96′ of FIG. 8A. Similarly, FIG. 8D isa schematic drawing illustrating a front view of a band frame 96″ (notshown with metallized dielectric honeycomb filter 50), where the bandframe has vertical spring fingers 100″, attached, for example, to a band98 at one end and oriented for vertical insertion. FIG. 8E is aschematic drawing illustrating a side view of the band frame 96″ of FIG.8D.

FIG. 8G is a schematic drawing illustrating a front view of the bandframe 96′″ of FIG. 8F, where the band frame 96′″ has elongatedconductive protrusions, or dimples 101′, extending outward from theperimeter. FIG. 8H is a schematic drawing illustrating a side view ofthe band frame 96′″ of FIG. 8H in which the band frame 96′″ haselongated dimples 101′. Similarly, FIG. 8I is a schematic drawingillustrating a front view of a band frame 96″″ (not shown withmetallized dielectric honeycomb filter 50), where the band frame 96″″has circular dimples 101″ formed, for example, within a band 98″″. FIG.8H is a schematic drawing illustrating a side view of the band frame96″″ of FIG. 8I.

In yet another embodiment, in a slim frame configuration, shown in FIG.8K, the band 99 98 uses a band frame 96 and incorporates narrow featuresor tabs 102 that wrap around the metallized dielectric honeycomb filter50 on its top and/or bottom surface a small amount, such as less thanabout 0.25 inch. Additionally, the tabs 102 can be cut away insubstantial areas, such that they only wrap around portions of themetallized dielectric honeycomb filter 50 on its top and/or bottomsurface. This embodiment provides additional support for the metallizeddielectric honeycomb filter 50 while only reducing the airflow surfaceby a small amount.

FIG. 8L is a schematic drawing illustrating a front view of one side ofthe band frame 96 of FIG. 8K, where the band frame has tabs 102 that arefashioned to bend such that when bent inward 90 degrees about eithersurface of the filter 50, the tabs secure the band frame 96 to thefilter 50. FIG. 8M is a schematic drawing illustrating a side view ofone side of the band frame 96 of FIG. 8L.

In yet further embodiments, the band frame 96 may be constructed fromany conductive material that maintains maximum air flow area through thedielectric honeycomb filter 50, but in addition to being electricallyconductive, can also help to accommodate variations in dimensionaltolerances during insertion of the dielectric honeycomb filter 50 intothe cabinet 20. Dimensional tolerances between the dielectric honeycombfilter 50 and the enclosure 20 can be accommodated, for example, byusing conductive foam, conductive fabric, or conductive fabric wrappedfoam for the band material. These band materials create good electricalcontact just like a metal band, but unlike a metal band, these bandmaterials have a much lower compression force and are more compliantallowing them to readily accommodate tolerance variations between themetallized dielectric honeycomb filter 50 and the cabinet 20. Conductivefabric wrapped foams and conductive foams can be obtained from LairdTechnologies, Inc., located in Delaware Water Gap, Pa.

In one embodiment, illustrated in FIG. 9, the conductive foam or theconductive fabric wrapped foams 104 for use as a band 98 can be slit ormanufactured into strips that are approximately as wide or wider as themetallized dielectric honeycomb filter 50 is thick. The strips of theseband materials 104 can then be applied to the perimeter of themetallized dielectric honeycomb filter 50 by using an adhesiveattachment method, such as pressure sensitive adhesive or glue 106, toform a complete band around the periphery of the metallized dielectrichoneycomb filter 50. The thicknesses of these band materials can varyfrom about 0.5 millimeter to about 10 millimeter, or as needed to fillthe gaps between the metallized dielectric honeycomb filter 50 and theenclosure 20. These band materials 104 have the advantages of beingelectrically conductive, flexible and easily compressed, making themuseful as an EMI seal/gasket between the metallized dielectric honeycombfilter 50 and the cabinet 20. This allows the EMI radiation inducedelectrical currents to flow readily from the metallized dielectrichoneycomb filter 50 through the band material, to the cabinet 20, andthen finally to ground. The compressible foam material fills the gapsand maintains a good compression fit between the metallized dielectrichoneycomb filter 50 and the cabinet 20, while sealing any surfacediscontinuities, seams, and gaps that could act as EMI leakage points.

As readily understood by those skilled in the art, many differentconfigurations can be used to contain the metallized dielectrichoneycomb filter 50 in the enclosure 20.

The metallized dielectric honeycomb filter 50 provides improved airflowwhile meeting stringent flammability standards. Once One suchflammability standard is the UL94 Vertical Flame Test, described indetail in Underwriter Laboratories Standard 94 entitled “Tests forFlammability of Plastic Materials for Parts in Devices and Appliances,”5^(th) Edition, 1996, the disclosure of which is incorporated herein byreference in its entirety. The metallized dielectric vent panels 50according to the invention are able to achieve V0 flame rating, as wellas V1 and V2 vertical ratings described in the standard.

EMI shielding effectiveness and airflow test data for a metallizeddielectric honeycomb filter in accordance with certain embodiments ofthe invention are shown respectively in FIGS. 10 and 11. The filtertested for shielding effectiveness is made of a polycarbonate polymerwith a plating of nickel over copper. The test panel is about 0.5 inchesthick, with a cell size of about 0.125 inches, and a density of about 4lb/ft³. The nickel layer is about 5-10 micro inches thick and wasapplied by electroless plating. The copper layer is about 20-50 microinches thick and was applied by electroless plating. FIG. 10 shows thatin the frameless configuration, the metallized dielectric honeycombfilter provides a range of about 80-90 dB of shielding effectiveness upto 1 GHz. In the framed configuration, the nickel over copper metallizeddielectric honeycomb filter provides a range of about 40-60 dB ofshielding effectiveness up to 1 GHz. FIG. 10 also provides test resultsfor traditional aluminum honeycomb vent panels with different finishes(bare and chromated). The aluminum vent panels with no plating and withchromate finish provide only 30-40 dB of shielding effectiveness up to 1GHz.

The filters tested for airflow effectiveness are the standard aluminumhoneycomb and two different polycarbonate polymer honeycombs with aplating of nickel over copper in accordance with the invention. The testpanels were about 0.5 inch thick with a cell size of about 0.125 inch.One of the dielectric honeycomb panels had a density of about 4 lb/ft³and the other dielectric honeycomb panel had a density of about 10lb/ft³. FIG. 11 shows that there is substantially no difference inairflow characteristics between standard aluminum honeycomb of the samethickness and cell size and the 4 or 10 lb/ft³ density of the metallizeddielectric honeycomb. All of the air flow testing was conducted on thehoneycomb without the presence of a frame, so that the results representthe air flow performance of the honeycomb materials.

Accordingly, vent panels produced in accordance with the invention canyield significantly improved shielding effectiveness for the sameairflow characteristics as conventional metal vent panels.

Variations, modifications, and other implementations of what isdescribed herein will occur to those of ordinary skill in the artwithout departing from the spirit and the scope of the invention asclaimed. The various features and configurations shown and equivalentsthereof can be used in various combinations and permutations.Accordingly, the invention is to be defined not by the precedingillustrative descriptions, but instead by the following claims.

1. A frameless vent panel adapted to shield against electromagneticinterference (EMI) comprising: a dielectric panel having a thicknessdefined by a first side and a second side, and defining a plurality ofapertures, said dielectric panel further having a perimeter; a firstelectrically conductive layer applied to the dielectric pane, whereinthe conductively coated dielectric panel attenuates a transfer ofelectromagnetic energy from the first side to the second side of thesubstrate; and a strip of compressible conductive foam material, saidstrip having a width substantially equal to the thickness of saiddielectric panel and being wrapped around the perimeter thereof andsubstantially covering said thickness between said first side and saidsecond side.
 2. The frameless vent panel of claim 1, wherein thedielectric panel is of a polymer.
 3. The frameless vent panel of claim1, wherein the dielectric panel is of a material selected from the groupconsisting of polycarbonate, polypropyle ,acrylonitrile-butadiene-styrene (ABS), polyethylene, polyvinyl chloride(PVC), carbon, fiberglass, paper and combinations thereof.
 4. Theframeless vent panel of claim 1, wherein the dielectric panel comprisesa plurality of tubes bonded together.
 5. The frameless vent panel ofclaim 1, wherein the dielectric panel comprises a plurality of tubesco-extruded together.
 6. The frameless vent panel of claim 1, whereinthe dielectric panel is produced using an injection molding process. 7.The frameless vent panel of claim 1, wherein the dielectric panelcomprises a plurality of corrugated dielectric sheets bonded together,wherein the bonded corrugated dielectric sheets define the plurality ofapertures.
 8. The frameless vent panel of claim 1, wherein theelectrically conductive layer is of a material selected from the groupconsisting of copper, nickel, tin, aluminum, silver, gold, graphite,lead, palladium, cadmium, zinc and combination thereof.
 9. The framelessvent panel of claim 1, further comprising a second electricallyconductive layer in electrical communication with the first electricallyconductive layer.
 10. The frameless vent panel of claim 1, wherein theplurality of apertures is configured as a two-dimensional array of likeapertures.
 11. The frameless vent panel of claim 10, wherein across-sectional shape of each of the like apertures is a shape selectedfrom the group consisting of circular, elliptical, hexagonal, square,rectangular, triangular, rhomboidal, and combinations thereof.
 12. Theframeless vent panel of claim 1, wherein a cross-sectional diameter ofeach of the like apertures is selected to be between about 0.06 inchesand 1 inch.
 13. The frameless vent panel of claim 1, wherein thedielectric panel is selected to have a density of between about 2 lb/ft³and about 20 lb/ft³.
 14. The frameless vent panel of claim 1, whereinthe vent panel provides at least about 20 dB of attenuation to EMI at10⁹ Hz.
 15. The frameless vent panel of claim 1, wherein said stripcompressible conductive foam is secured to said dielectric panel with anadhesive.
 16. The frameless vent panel of claim 1, wherein said strip ofcompressible conductive foam has a thickness in a range from about 0.5millimeter to about 10 millimeters.
 17. A frameless vent panel forproviding electromagnetic interference (EMI) shielding for a ventilationopening of an electronic enclosure, the frameless vent panel comprising:a dielectric panel having a thickness defined by a first side and asecond side, a perimeter, and a plurality of apertures extending fromthe first side to the second side for allowing airflow therethrough; atleast one electrically-conductive material provided to the dielectricpanel for attenuating a transfer of electromagnetic energy from thefirst side to the second side; and a resiliently compressibleelectrically-conductive edge substantially about the perimeter of theframeless vent panel and substantially covering said thickness betweensaid first side and said second side, for compressively fitting theframeless vent panel within the ventilation opening in electricalcommunication with the electronic enclosure.
 18. The frameless ventpanel of claim 17, wherein the resiliently compressibleelectrically-conductive edge is configured for allowing the framelessvent panel to be compressively fit and retained within the ventilationopening without using any mechanical fasteners.
 19. The frameless ventpanel of claim 17, wherein the resiliently compressibleelectrically-conductive edge is configured for allowing the framelessvent panel to be compressively fit and retained within the ventilationopening in a direction normal to the longitudinal axes of the apertures.20. The frameless vent panel of claim 17, wherein the resilientlycompressible electrically-conductive edge comprises a band of one ormore materials, the band having a width substantially equal to thethickness of the dielectric panel and being wrapped around the perimeterof the dielectric panel such that the band substantially covers thethickness defined between the first side and the second side.
 21. Theframeless vent panel of claim 20, wherein the band of one or morematerials comprises at least one or more of electrically-conductivefoam, electrically-conductive fabric, and electrically-conductive fabricwrapped over foam.
 22. The frameless vent panel of claim 17, wherein theresiliently compressible electrically-conductive edge compriseselectrically-conductive fabric.
 23. The frameless vent panel of claim17, wherein the resiliently compressible electrically-conductive edgecomprises electrically-conductive fabric wrapped over foam.
 24. Theframeless vent panel of claim 17, wherein the resiliently compressibleelectrically-conductive edge comprises electrically-conductive foam. 25.The frameless vent panel of claim 17, wherein the resilientlycompressible electrically-conductive edge comprises a resilientlycompressible EMI gasket having a width substantially equal to thethickness of the dielectric panel, the resiliently compressible EMIgasket being wrapped around the perimeter of the dielectric panel suchthat the resiliently compressible EMI gasket substantially covers thethickness defined between the first side and the second side.
 26. Theframeless vent panel of claim 17, wherein the resiliently compressibleelectrically-conductive edge comprises electrically-conductiveelastomer.
 27. The frameless vent panel of claim 17, wherein theresiliently compressible electrically-conductive edge compriseselectrically-conductive protrusions extending outwardly substantiallyabout the perimeter.
 28. The frameless vent panel of claim 27, whereinthe electrically-conductive protrusions comprise at least one or more ofa resilient spring finger, a dimple, or a combination thereof.
 29. Theframeless vent panel of claim 17, wherein the resiliently compressibleelectrically-conductive edge comprises electrically-conductive wiremesh.
 30. The frameless vent panel of claim 17, wherein the resilientlycompressible electrically-conductive edge compriseselectrically-conductive material disposed over a resilientlycompressible member.
 31. The frameless vent panel of claim 17, whereinthe resiliently compressible electrically-conductive edge compriseselectrically-conductive fabric applied to an elastomer.
 32. Theframeless vent panel of claim 17, wherein the openings have a honeycombconfiguration.
 33. The frameless vent panel of claim 17, furthercomprising flame retardant provided to the conductively coateddielectric panel for achieving a flame rating of V0 under Underwriter'sLaboratories (UL) Standard No.
 94. 34. The frameless vent panel of claim17, further comprising a corrosion inhibitor provided to theconductively coated dielectric panel.
 35. A frameless vent panel forproviding electromagnetic interference (EMI) shielding for a ventilationopening of an electronic enclosure, the frameless vent panel comprising:a frameless dielectric panel having a thickness defined by a first sideand a second side, a perimeter, and a plurality of apertures extendingfrom the first side to the second side for allowing airflowtherethrough; at least one electrically-conductive material provided tothe frameless dielectric panel for attenuating a transfer ofelectromagnetic energy from the first side to the second side; and aresiliently compressible EMI gasket having a width substantially equalto the thickness of the frameless dielectric panel, the resilientlycompressible EMI gasket being wrapped around the perimeter of theframeless dielectric panel and substantially covering the thicknessdefined between the first side and the second side.
 36. The framelessvent panel of claim 35, wherein the resiliently compressible EMI gasketcomprises electrically-conductive fabric wrapped over foam.
 37. Theframeless vent panel of claim 35, wherein the resilient compressible EMIgasket comprises electrically-conductive material coupled to aresiliently compressible member.
 38. A frameless vent panel forproviding electromagnetic interference (EMI) shielding for a ventilationopening of an electronic enclosure, the frameless vent panel comprising:a dielectric panel having a thickness defined by a first side and asecond side, a perimeter, and a plurality of apertures extending fromthe first side to the second side for allowing airflow therethrough; atleast one electrically-conductive material provided to the dielectricpanel for attenuating a transfer of electromagnetic energy from thefirst side to the second side; and means for compressively fitting andretaining the frameless vent panel within the ventilation opening andfor placing the frameless vent panel in electrical communication withthe electronic enclosure, said means disposed substantially about theperimeter of the frameless vent panel with said means substantiallycovering the thickness defined between the first side and the secondside.
 39. An electronic enclosure comprising: a ventilation opening; aframeless vent panel within the ventilation opening for providingelectromagnetic interference (EMI) shielding, the frameless vent panelincluding: a dielectric panel having a thickness defined by a first sideand a second side, a perimeter, and a plurality of apertures extendingfrom the first side to the second side for allowing airflowtherethrough; at least one electrically-conductive material provided tothe dielectric panel for attenuating a transfer of electromagneticenergy from the first side to the second side; and a resilientlycompressible electrically-conductive edge substantially about theperimeter of the frameless vent panel and substantially covering thethickness defined between the first side and the second side, theresiliently compressible electrically-conductive edge compressivelyretaining the frameless vent panel within the ventilation opening inelectrical communication with the electronic enclosure.
 40. Theelectronic enclosure of claim 39, wherein the frameless vent panel iscompressively retained within the ventilation opening by the resilientlycompressible electrically-conductive edge without using any mechanicalfasteners.
 41. The electronic enclosure of claim 39, wherein theresiliently compressible electrically-conductive edge is compressedwithin the ventilation opening in a direction normal to the longitudinalaxes of the apertures.
 42. The electronic enclosure of claim 39, whereinthe resiliently compressible electrically-conductive edge comprises aband of one or more materials, the band having a width substantiallyequal to the thickness of the dielectric panel and being wrapped aroundthe perimeter of the dielectric panel such that the band substantiallycovers the thickness defined between the first side and the second side.43. The electronic enclosure of claim 42, wherein the band of one ormore materials comprises at least one or more of electrically-conductivefoam, electrically-conductive fabric, and electrically-conductive fabricwrapped over foam.
 44. The electronic enclosure of claim 39, wherein theresiliently compressible electrically-conductive edge compriseselectrically-conductive fabric wrapped over foam.
 45. The electronicenclosure of claim 39, wherein the resiliently compressibleelectrically-conductive edge comprises a resiliently compressible EMIgasket having a width substantially equal to the thickness of thedielectric panel and being wrapped around the perimeter of thedielectric panel such that the resiliently compressible EMI gasketsubstantially covers the thickness defined between the first side andthe second side.
 46. A method for electromagnetic interference (EMI)shielding a ventilation opening of an electronic enclosure, the methodcomprising positioning a frameless metallized dielectric vent panelwithin the ventilation opening such that the frameless metallizeddielectric vent panel is compressively retained within the ventilationopening by a resiliently compressible electrically-conductive edgedisposed substantially about the perimeter of the frameless metallizeddielectric vent panel and substantially covering the thickness definedbetween a first side and a second side of the frameless metallizeddielectric vent panel, and such that the resiliently compressibleelectrically-conductive edge places the frameless metallized dielectricvent panel in electrical communication with the electronic enclosure.47. The method of claim 46, wherein the frameless metallized dielectricvent panel is compressively retained within the ventilation opening bythe resiliently compressible electrically-conductive edge without usingany mechanical fasteners.
 48. The method of claim 46, wherein theframeless metallized dielectric vent panel includes a plurality ofapertures extending from the first side to the second side for allowingairflow therethrough, and wherein positioning the frameless metallizeddielectric vent panel within the ventilation opening includescompressing the resiliently compressible electrically-conductive edgewithin the ventilation opening in a direction generally perpendicular tothe longitudinal axes of the apertures.
 49. A method of making aframeless vent panel capable of providing electromagnetic interference(EMI) shielding for a ventilation opening of an electronic enclosure,the method comprising providing a frameless metallized dielectric ventpanel with a resiliently compressible electrically-conductive edgesubstantially about a perimeter of the frameless metallized dielectricvent panel such that the resiliently compressibleelectrically-conductive edge substantially covers a thickness definedbetween a first side and a second side of the frameless metallizeddielectric vent panel, the resiliently compressibleelectrically-conductive edge being configured for allowing the framelessvent panel to be compressively fit and retained within the ventilationopening in electrical contact with the electronic enclosure.
 50. Themethod of claim 49, further comprising metalizing a dielectric panel tothereby create the frameless metallized dielectric vent panel beforeproviding the frameless metallized dielectric vent panel with theresiliently compressible electrically-conductive edge.
 51. The method ofclaim 49, wherein providing the frameless metallized dielectric ventpanel with the resiliently compressible electrically-conductive edgecomprises positioning a band of one or more materials about theperimeter of the frameless metallized dielectric vent panel such thatthe band of one or more materials substantially covers the thicknessdefined between the first side and said second side.
 52. The method ofclaim 51, wherein the band of one or more materials comprises at leastone or more of electrically-conductive foam, electrically-conductivefabric, and electrically-conductive fabric wrapped over foam.
 53. Themethod of claim 49, wherein providing the frameless metallizeddielectric vent panel with the resiliently compressibleelectrically-conductive edge comprises positioningelectrically-conductive fabric wrapped over foam about the perimeter ofthe frameless metallized dielectric vent panel such that theelectrically-conductive fabric wrapped over foam substantially coversthe thickness defined between the first side and said second side. 54.The method of claim 50, wherein providing the frameless metallizeddielectric vent panel with the resiliently compressibleelectrically-conductive edge comprises positioningelectrically-conductive fabric about the perimeter of the framelessmetallized dielectric vent panel such that the electrically-conductivefabric substantially covers the thickness defined between the first sideand said second side.
 55. The method of claim 49, wherein providing theframeless metallized dielectric vent panel with the resilientlycompressible electrically-conductive edge comprises positioningelectrically-conductive foam about the perimeter of the framelessmetallized dielectric vent panel such that the electrically-conductivefoam substantially covers the thickness defined between the first sideand said second side.
 56. The method of claim 49, wherein providing theframeless metallized dielectric vent panel with the resilientlycompressible electrically-conductive edge comprises positioning aresiliently compressible EMI gasket about the perimeter of the framelessmetallized dielectric vent panel such that the resiliently compressibleEMI gasket substantially covers the thickness defined between the firstside and said second side.
 57. The method of claim 49, wherein providingthe frameless metallized dielectric vent panel with the resilientlycompressible electrically-conductive edge comprises positioningelectrically-conductive elastomer about the perimeter of the framelessmetallized dielectric vent panel such that the electrically-conductiveelastomer substantially covers the thickness defined between the firstside and said second side.
 58. The method of claim 49, wherein providingthe frameless metallized dielectric vent panel with the resilientlycompressible electrically-conductive edge comprises providing edgetreatment to the frameless metallized dielectric vent panel to createelectrically-conductive protrusions extending outwardly substantiallyabout the perimeter of the metallized dielectric vent panel.
 59. Themethod of claim 58, wherein the electrically-conductive protrusionscomprise at least one or more of a resilient spring finger, a dimple, ora combination thereof.
 60. The method of claim 49, wherein providing theframeless metallized dielectric vent panel with the resilientlycompressible electrically-conductive edge comprises positioning anelectrically-conductive wire mesh about the perimeter of the framelessmetallized dielectric vent panel such that the electrically-conductivewire mesh substantially covers the thickness defined between the firstside and said second side.
 61. The method of claim 49, furthercomprising providing the frameless metallized dielectric vent panel withflame retardant sufficient for achieving a flame rating of V0 underUnderwriter's Laboratories (UL) Standard No.
 94. 62. The method of claim49, further comprising providing the frameless metallized dielectricvent panel with a corrosion inhibitor.
 63. The method of claim 49,further comprising applying at least one coating to the frameless ventpanel for enhancing at least one performance attribute of the framelessvent panel.
 64. The method of claim 63, wherein the coating comprises atleast one or more of a mildew inhibitor, a corrosion inhibitor, and aflame retardant.